assume cs:codesg

codesg segment
        mov ax, 4C00H
        int 21H

start:  mov ax, 0
    s:  nop
        nop

        mov di, offset s
        mov si, offset s2
        mov ax, cs:[si]
        mov cs:[di], ax

   s0:  jmp short s
   s1:  mov ax, 0
        int 21h
        mov ax, 0
   s2:  jmp short s1
        nop
codesg ends

end start
